Glowplug with greatly shortened control coil

ABSTRACT

A sheathed-element glow plug for an internal combustion engine, in which the sheathed-element glow plug is arranged or constructed so that it substantially reduces the glow temperature during the heat-up process. The control filament is considerably shortened and has a resistance between 20 mΩ and 100 mΩ.

FIELD OF THE INVENTION

The present invention relates to a sheathed-element glow plug for aninternal combustion engine, having a plug housing, a terminal deviceconnected to the plug housing for the glow current, a glow tubeconnected to the terminal device, which is sealed on its side facingaway from the plug housing, a wire filament-shaped resistor elementprovided on the terminal stud connected to the terminal device in theglow tube, the resistor element being composed of a heating filament anda control filament.

BACKGROUND INFORMATION

There are sheathed-element glow plugs for diesel engines. Suchsheathed-element glow plugs are operated at vehicle electrical systemvoltages of approximately 11 V for pre-glow and approximately 14 V for arunning engine. These sheathed-element glow plugs are controlled by aglow time controller without voltage-reducing measures. This means thatthe sheathed-element glow plugs are intrinsically safe and they regulatethe current during heat-up in such a way that no critical temperaturesare exceeded.

European patent document no. 1 034 400 discusses such sheathed-elementglow plugs having a reduced control filament portion. This controlfilament portion is defined such that, when operated using vehiclesystem voltages, the sheathed-element glow plug cannot be regulated downto operating temperature, but is operated at a temperature which ishigher than the admissible temperature. The design of the controlfilament causes the sheathed-element glow plug to heat up the combustionchamber of an internal combustion engine very rapidly. The operatingtemperature is regulated by the glow time controller, which sets thevoltage via timing (pulse-width modulation).

SUMMARY OF THE INVENTION

An object of the exemplary embodiment and/or exemplary method of thepresent invention is to further reduce the heat-up time of thesheathed-element glow plug. A voltage dip of the vehicle system voltagewhen the engine is started should not result in a temperature dip of thesheathed-element glow plug.

The exemplary embodiment and/or exemplary method of the presentinvention is intended to further considerably reduce the glow time bydesigning the control filament portion to be substantially shorter andsetting its resistance to a few mQ.

Therefore, with the exemplary embodiment and/or exemplary method of thepresent invention the control filament has a resistance between 20 mΩand 100 mΩ.

Designing the control filament to have such a low resistance, which maybe in the range between 20 mΩ and 100 mΩ, reduces the nominal voltage(the voltage at which the sheathed-element glow plug reaches itsoperating temperature).

This reduces the heat-up time of the sheathed-element glow plug fromapproximately 6 seconds to 2 seconds, which is intended to provide asignificantly quicker start of the diesel engine.

Another advantage results from the fact that, by reducing the nominalvoltage, the effective voltage may be controlled by a glow timecontroller in such a way that no temperature dip of the sheathed-elementglow plug occurs during the voltage dip when the internal combustionengine is started. As a result, the diesel engine starts considerablymore rapidly and reliably. In addition, the engine ramps up to idlingspeed more rapidly and reliably.

In the warm-up phase of the engine, the temperature of thesheathed-element glow plug may be kept at the appropriate level byadjusting the pulse rate of the glow time controller. This makes theidling of the cold engine quieter, while reducing harmful emissions. Byswitching to overrun in a controlled manner, harmful emissions may bereduced when the accelerator is pressed again.

The heated zone of the sheathed-element glow plug is reduced (due to thecompact design of the control filament), so that only the area of thesheathed-element glow plug actually protruding into the combustionchamber is heated. The electrical balance of the vehicle is thusimproved and engine fuel is saved.

Due to the considerably shortened control filament portion, thesheathed-element glow plug responds, even when warm or hot, to anincrease in voltage very rapidly. This is intended to provide promptadjustment of the sheathed-element glow plug temperature to therequirements of the diesel engine.

According to the exemplary embodiment and/or exemplary method of thepresent invention, the shortened area of the control filament may havedifferent designs.

One end of the control filament is connected to a terminal stud, whichis in turn electrically connected to the terminal device. The terminalstud is either inserted far into the heating area in the glow tube or,as an alternative, the terminal stud may use an available arrangementand the control filament may have an appropriately low resistance usingunwound wire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section of a sheathed-element glow plug as known from therelated art.

FIG. 2 shows a section of a first exemplary embodiment of asheathed-element glow plug having a shortened control filament accordingto the present invention.

FIG. 3 shows a section of a second exemplary embodiment of asheathed-element glow plug according to the present invention in whichthe heating filament is connected to the terminal stud by a straightelement made of the same material.

DETAILED DESCRIPTION

FIG. 1 shows the sheathed-element glow plug from the related art. Thissheathed-element glow plug 1 includes a plug housing 2. A terminaldevice 3 via which the glow current is supplied to sheathed-element glowplug 1 is provided in plug housing 2. Furthermore, a glow tube 4, whichis connected to terminal device 3, is provided. A resistor element 5 isprovided in glow tube 4, resistor element 5 being divided into twoareas: a heating filament 6 and a control filament 7. Heating filament 6is connected (welded) to control filament 7. The end of control filament7 opposite heating filament 6 is connected to a terminal stud 9,terminal stud 9 being designed as part of the terminal device, the glowcurrent thus being supplied via terminal stud 9 to control filament 7and heating filament 6.

In the exemplary embodiment of the present invention depicted in FIG. 2,terminal stud 9 has a considerably longer design within glow tube 4according to the exemplary embodiment and/or exemplary method of thepresent invention, so that control filament 7 has a very short design.

FIG. 3, as an alternative to FIG. 2, depicts terminal stud 9 of a designcomparable to that of the related art, heating filament 6 being directlyconnected to terminal stud 9. The straight piece is made of the samematerial as heating filament 6.

1-8. (canceled)
 9. A sheathed-element glow plug for an internalcombustion engine, comprising: a plug housing; a terminal deviceconnected to the plug housing for a glow current; a glow tube connectedto the terminal device and sealed at its end facing away from the plughousing; and a wire filament-shaped resistor element positioned in theglow tube on a terminal stud connected to the terminal device, whereinthe resistor element being includes a heating filament and a controlfilament, and the control filament has a resistance between 20 mΩ and100 mΩ.
 10. The glow plug of claim 9, wherein the resistor element inthe glow tube is concentrated in an area of an end of the glow tubefacing away from the plug housing, and wherein the resistor elementoccupies one-third to two-thirds of a free length of the glow tube. 11.The glow plug of claim 10, wherein the terminal stud extends into anarea situated within a combustion chamber of the internal combustionengine.
 12. The glow plug of claim 10, wherein a path between theterminal stud, which is located in the plug housing, and the heatingfilament is bridged by a straight piece of wire, which is made of thesame material as the control filament remote from a combustion chamberof the internal combustion engine.
 13. The glow plug of claim 9, whereinthe control filament is located at a tip of the glow tube, and theheating filament is located in a part of the glow tube remote from thecombustion chamber of the internal combustion engine.
 14. Asheathed-element glow plug for an internal combustion engine,comprising: a plug housing; a terminal device connected to the plughousing for a glow current; a glow tube connected to the terminal deviceand sealed at its end facing away from the plug housing; and a wirefilament-shaped resistor element positioned in the glow tube on aterminal stud connected to the terminal device, wherein the resistorelement includes only one heating filament.
 15. The glow plug of claim14, wherein the terminal stud extends up to an end of the heatingfilament remote from a combustion chamber of the internal combustionengine.
 16. The glow plug of claim 14, wherein a path between theheating filament and the terminal stud, situated within the plughousing, is bridged by a straight element made of the same material asthe heating filament.